1. Field of the Invention
The present invention relates to a method of controlling the feed of yarn and a device for controlling the feed of yarn.
2. Description of the Prior Art
In a conventional tufting machine there has been provided one method of decorating with patterns by changing the height of yarn. Thus, it is necessary to control the feed yarn during one stitch of a needle and change the height of the yarn provided. There are various methods used for the control of the feed of yarn which can be classified by the following two types of methods of (1) changing the feed speed of the yarn and (2) changing the feed lapse time of the yarn.
As an ordinary method of changing the feed speed of yarn, there has been provided a method of changing the speed of the feed drum in two steps consisting of a high speed and a low speed. However, in this ordinary method, a drawback exists in that various changes can not be offered as only two steps of change are possible in this method.
As an ordinary method of changing the feed lapse of time of yarn, there has been provided a method of controlling the rotation period of a yarn feed drum by using a pulse motor as the driving power. However, in this ordinary method, there occurs a drawback in that the composition of the device for operation in this method is necessarily very complex, the technique for controlling the feed quantity of yarn is difficult, the control as a whole of the plurality of elements of the device of the method is very difficult, and maintenance thereof is troublesome since the durability of the device is low.
The present invention is a result of research with respect to various ways of deleting the defects described above and a manner of controlling a device for feed quantity regulation of yarn without controlling the driving power portion thereof. The method and apparatus of the present invention can obtain the necessary feed quantity of yarn by the control of a mean rotational frequency of yarn feed drum during one stitch by changing the rate of the periods in which two kinds of driving bodies are respectively driven with respective predetermined speeds during one stitch of a needle.